A number of carbapenams and carbapen-2-ems have been described in the literature--some of which have been reported to possess utility as antibacterial agents. Among the latter are a variety of fermentation derived products, the first of which was thienamycin: ##STR1## [Albers-Schonberg et al., J. Am. Chem. Soc. 100, 6491 (1978)]. Other compounds in this family of fermentation products include olivanic acids: ##STR2## [Brown et al., J. Chem. Soc. Chem. Commun., 523 (1977); Corbett et al., ibid. 953 (1977)], and a compound designated as PS-5: ##STR3## [Okamura et al., J. Antibiotics 31, 480 (1978)]. Subsequently a number of derivatives of thienamycin have been disclosed as having useful antibacterial activity, including the carbapen-2-em and carbapenam derivatives: ##STR4## Belgian Pat. No. 867,227) wherein R.sup.b is broadly defined to include hydrogen, acetyl and benzyloxycarbonyl and R.sup.c is broadly defined to include hydrogen and conventional carboxy protecting groups, such as benzhydryl and 2-naphthylmethyl (selectively removed by hydrogenolysis), 2,2,2-trichloroethyl (selectively removed by mild zinc reduction) and various 1-alkoxycarbonyloxyalkyl groups (selectively hydrolyzed under physiological conditions).
Thienamycin has also been prepared by total synthesis [Johnston et al., J. Am. Chem. Soc. 100, 313 (1978)], as have an ester precursor [Kametani et al., Heterocycles 12 (9), 1189 (1979)] and a number of other carbapenams and carbapen-2-ems, including carbapenam itself [Wong et al., J. Am. Chem. Soc. 99, 2823 (1977); Busson and Vanderhaeghe, J. Org. Chem. 43, 4438 (1978)], p-nitrobenzyl and 2,3-dihydro-3-oxobenzo[c]furan-1-yl-6-carboxylates [Onoue et al., Tetrahedron Letters (40), 3867 (1979)], 3-methylcarbapenam [Aida et al., Tetrahedron Letters (52), 4993 (1979)], p-nitrobenzyl 2-methylcarbapen-2-em-3-carboxylate [Baxter et al., J. Chem. Soc. Chem. Commun., 236 (1979)], sodium carbapen-2-em-3-carboxylate and sodium 6-(1-hydroxyethyl)carbapen-2-em-3-carboxylate [Cama and Christensen, J. Am. Chem. Soc. 100, 8006 (1978)], benzyl 2-oxocarbapenam-3-carboxylate and 2-(4-methylphenylsulfonyloxy)carbapen-2-em-3-carboxylate [Ratcliffe et al., Tetrahedron Letters (21), 31 (1980)]. Also disclosed in the literature are carbaceph-3-ems such as 7-acylamino-2-alkylcarbaceph-3-em-4-carboxylic and 7-acylamino-2-acyloxycarbaceph-3-em-4-carboxylic acid esters which are hydrolyzed in vivo, i.e. under physiological conditions (Belgian Pat. No. 875,054). In no case are these compounds derived by rearrangement of conventional beta-lactam derivatives nor are any of these compounds substituted at the 1-position.
Most recently, preparation of compounds of the structure ##STR5## have been described (Christensen et al., U.S. Pat. No. 4,208,422). In these compounds R.sup.c is substituted or unsubstituted alkyl, aryl or aralkyl. The multistep syntheses of these compounds from an alpha, beta-unsaturated aldehyde, viz., ##STR6## does not permit synthesis of the compounds of the present invention.
As a matter of simplicity, clarity and convenience, the nomenclature and ring number system generally employed herein is the standard "pen/ceph" nomenclature of the literature, e.g. ##STR7## An alternative name for carbapenam, also found in the literature, is 1-azabicyclo[3.2.0]heptan-7-one.